Apatite is the name applied to a group of calcium phosphate minerals containing other elements or radicals. The mineral occurs in the United States mainly in the form of the calcium phosphate ores that are referred to generically as phosphate rock. Phosphate rock is rock that consists of calcium phosphate largely in the form of the aforementioned apatite together with clay, quartz, and other non-valuable minerals, and is useful in fertilizers and as a source of phosphorus compounds. It occurs in large beds in the southeastern and the northwestern U.S.
The calcium phosphate is normally separated from other constituents of the ore by froth flotation. The de-slimed and sized calcium phosphate is floated from a slurry by aeration with the aid of one or more flotation agents. Most widely used flotation agents/collectors are the unsaturated fatty acids, for example, oleic acid, and the technical grades or commercial grades of naturally-occurring fatty acid mixtures having a high proportion of unsaturated fatty acids derived from such oils as such as tall oil, corn oil, safflower oil, soybean oil, cottonseed oil, and linseed oil, and derivatives thereof, as well as synthetic acids. The flotation effect of the fatty acids is usually enhanced by mixing in a similar amount of a petroleum-based hydrocarbon, such as diesel oil, #5 fuel oil, or reclaimed oil, which sometimes contains a small amount of a nonionic or anionic emulsifier. The use of such petroleum-based hydrocarbons is causing concern because eventually part of the process water and all of the flotation “tailings” are returned to the environment whereby the petroleum hydrocarbons could enter waterways and aquifers. Unlike the fatty acid based components, fuel oil and reclaimed oils may contain fractions that are non-biodegradable and can contain hazardous polynuclear aromatics.